This invention relates to a method for forming a thermistor thin film. More specifically, it relates to a thermistor thin film suitable for a heat sensitive resistor film for an NTC thermistor.
Heretofore, a manganese-cobalt oxide thin film has been used for this purpose. Such a film has been formed by a dry method on the surface of a substrate, by sputtering using a composite oxide containing manganese and cobalt as a target material (National Technical Report, Vol. 29, No. 3, 1983). In a wet method, a methanol solution of a .beta.-diketonato complex containing three components of Mn-Co-Ni is coated on a glass or quartz substrate by dipping, and after calcinating at 450.degree. C., the coating and calcination are repeated to form a Mn-Co-Ni thin film (Masaharu Kaneko et al., 4th Japan Ceramic Association, Autumn Symposium, Preprint (1991), p. 140).
However, with the physical deposition method the sputtering method, it is difficult to obtain a dense and uniform manganese-cobalt oxide thin film over a wide range and the preparation cost becomes expensive.
In the wet method, when dissolving the .beta.-diketonato complex in the methanol solution, the precipitation rates of the respective components may not be uniform. It is also inconvenient in that the thin film composition may vary from the desired composition due to the difference in volatilities of the respective components at calcination.